September 11, 2013

A group of British scientists has for the first time found evidence of diverse lifeforms dating back nearly 100 thousand years in subglacial lake sediment.

For decades, scientists have been fascinated by the idea that extreme lifeforms might exist in the cold and dark lakes hidden miles beneath the Antarctic ice sheet. Direct sampling of these lakes in the interior of Antarctica, however, presents major technological challenges even today.

Because of these challenges, a group of scientists from the British Antarctic Survey (BAS), and the Universities of Northumbria and Edinburgh has been searching the retreating edges of the ice sheet for subglacial lakes. These lakes are becoming exposed for the first time since being buried over 100,000 years ago; parts of the ice sheet are melting and retreating at unprecedented rates as the temperature rises at the poles. The results of their study were published in the journal Diversity.

The researchers focused on Lake Hodgson on the Antarctic Peninsula. At the end of the last ice age, Lake Hodgson was covered by about 1300 feet of ice. Today, however, it is considered to be an emerging subglacial lake, with a thin covering of just 10-13 feet of ice.

The team drilled through the ice using clean coring techniques to delve into the sediments at the bottom of the lake, which is 305 feet deep and approximately one mile wide and long.

Lake Hodgson is believed to have been a harsh environment for any form of life but the layers of mud at the bottom of the lake represent a time capsule storing the DNA of the microbes that have lived there throughout the millennia. Current and recent organisms that inhabit the lake were contained in the top few centimeters of the core samples. However, the microbes found at 10 feet down most likely date back nearly 100,000 years.

"What was surprising was the high biomass and diversity we found. This is the first time microbes have been identified living in the sediments of a subglacial Antarctic lake and indicates that life can exist and potentially thrive in environments we would consider too extreme," said David Pearce, who was at BAS and is now at the University of Northumbria.

"The fact these organisms have survived in such a unique environment could mean they have developed in unique ways which could lead to exciting discoveries for us. This is the early stage and we now need to do more work to further investigate these life forms."

Some of the life the team uncovered was in the form of Fossil DNA that showed many different types of bacteria lived there, including a range of extremophiles - species adapted to the most extreme environments, typically sustaining life with and without oxygen using a variety of chemical methods.

One DNA sequence the team found was related to the most ancient organisms known on the planet. Parts of the DNA in 23 percent of the findings have not been previously described, meaning that many of the species are likely to be new to science making clean exploration of the remote lakes isolated under the deeper parts of the ice sheet even more pressing.

Scientists are hoping that clues for how life might survive on other planets could be hidden with organisms living in subglacial lakes.

Previous and current studies into subglacial lakes include a British expedition late last year to drill into Lake Ellsworth that was called off after technical difficulties; a US expedition sampled a subglacial environment near the edge of the ice sheet but has yet to report its findings; and a Russian-led project has sampled ice near the surface of subglacial Lake Vostok, which has also reported finding signs of life.